#pragma once
#include <string>
#include <iostream>
using namespace std;
class BieuThuc
{
protected:
	float k;
public:
	virtual BieuThuc& khoitao(float *x,int i)=0;
	virtual string bieuDien() = 0;
	virtual string bieuDienDaoHam() = 0;
	virtual float tinhGiaTri(float x) = 0;
	virtual float tinhDaoHam(float x) = 0;
	BieuThuc();
	~BieuThuc();
	
};
